Context: Pituitary adenoma is generally indolent, but an aggressive subtype called atypical adenoma has uncertain prognosis, and an unclear relationship between prognosis and morphology.

Objective: This study investigated the prognostic factors of this tumor. Design: Retrospective analysis. Setting: University and associated hospitals.

Inclusion Criteria:

• pituitary adenomas of more than 3 % of Ki67 labeling index surgically treated at Tohoku university and associated hospital

Exclusion Criteria:

• pituitary adenomas of less than 3 % of Ki-67 labeling index surgically treated at Tohoku university and associated hospital